Grace Design m903 Reference Headphone Amplifier, DAC, and Monitor Controller Balanced and unbalanced analog inputs;24bit/192kHz digital stereo inputs- AES3, S/PDIF, TOSLINK and USB High speed USB interface - completely asynchronous transfer mode allows for bit-perfect playback with zero interface induced jitter New generation DAC's and ultra low noise balanced current to voltage converter yields more musical performance compared to the m902 Driverless operation on Windows & Mac up to 96kHz/24bit; supports USB Class 2 audio specification for 192kHz/24bit operation on Windows & Mac (drivers needed for 192kHz operation under Windows) Internal linear power supply with custom wound toroidal transformer w/sealed gold contact relays used for all signal switching